1. Field of the Invention
The invention generally relates to alarm systems and specifically relates to alarm systems designed for rolling blinds.
2. Background Art
Rolling shutters are commonly used to cover windows, doors and other openings in private residences and in commercial buildings. They provide protection against intrusion and the resulting damage. A rolling shutter comprises the shutter frame, shutter rails, connected slats and a case that contains the rolled up connected slats. The slats are primarily made out of plastic or aluminum. The shutters open either manually or automatically. The rolling shutter can be partially closed; in that case, gaps remain between the honeycombed slats. There are two types of rolling shutters. One is a rolling shutter that is incorporated into the structure during construction, where the rails are physically connected to the structure and the shutter case is located inside the structure, this way there's no access to the rolling blinds case from the outside of the structure. The second type of rolling shutters is one that is mounted after the structure has been completed. In that case the rails are connected outside the structure and the shutter case is facing outside.
The rolling shutters provide a good solution for the covering of various windows, doorways and other openings. They also provide some protection against intrusion, but they are not resistant to a break in. It is possible to lift the slats from the outside. It is even possible to uproot the rails, in rolling shutters that are constructed after the structure has been completed. Portable battery powered power tools allow for the sawing of the slats, creating an opening allowing passage. Even the use of mechanical means designed to hinder intrusions, such as putting a lock on the bottom slat or adding a pin to guard from an outside lifting of the slats cannot prevent an intrusion. The rolling blinds are hindering intrusions, but cannot stop them. That's why an alarm system is needed, one that reports in the case of an intrusion attempt through the rolling shutter.
There are plenty of ways to add alarm sensors to a rolling shutter. The simplest way is to add a pushbutton at the bottom of the shutter frame. Normally the pushbutton is not pressed down and is its terminals are disconnected. When the rolling shutter is closed, the lowest slat presses the pushbutton, causing its terminals to be electrically connected. The pushbutton is connected to an alarm system that detects when the pushbutton is disconnects and operates the alarm. This method is not effective against an intruder who cuts the lowest slat, thus leaving the pushbutton pressed and fooling the system into thinking the shutter is closed. In other cases, a switch is operated by using a magnet that is attached to one of the rails, either on the inner or outer edge of the rail, and another magnet, which is attached to one of the slats; this alarm system also cannot detect an intruder who cuts the slats.
Patent application number DE4008441, titled “Roller shutter with transverse slats in side guides” describes a specialized rolling blind sensor, comprised of a two wires electrical cable that is threaded throw plurality of slats. The connection of the wires between each of the different slats is done by using a special connector. In the lowest slat the two wires of the cable are connected. The upper edges of the wires are connected through slip rings to the alarm system. The electric circuit will disconnect if an attempt will be made to cut the slats or to separate them; this system, though, does not provide warning in the case of an intruder who simply lifts the slats, and also does not provide a warning if a person forgot to lower the blinds altogether.
U.S. Pat. No. 6,054,921, titled “Alarm for a roll shutter assembly” describes a specialized sensor for rolling blinds that is based on a pressure sensor that is attached all along the shutter rail. This sensor does not identify the simple action of someone lifting the blinds and its installation is complex.
U.S. Pat. No. 4,232,309, titled “Roller shutter” describes a system based on magnetically operated switches. The switches are mounted inside the shutter rails in two different heights, one at the bottom and the other at the top of the rails. Fixed magnets are attached to the edges of the slats that will reach the same height as the magnets installed inside the rail when the shutter is closed. When the shutter is closed, the magnetically operated switches are activated, and generate closed current circuit. This system provides warning when attempt is made to lift the slats. However, it does not detect an attempt to cut the slats in the center of the shutter.
Hence, there is a need of a system that will provide reliable warnings against rolling blinds intrusion, in whatever method that intrusion is carried. This system should be easily installed over existing rolling blinds and should easily connect to existing alarm systems.